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Radio-controlled (or R/C) cars are
usually categorized as either "toy" or "hobby" grade. Remote
control vehicles are usually of one of two types: control of a
vehicle by radio transmission or by a wire connecting between the
transmitter and car. This article focuses on the radio-controlled
vehicle category, both toy and hobby grades.

In both of these categories, both on-road and off-road vehicles are available. Off-road
models, which are built with fully-functional off-road suspensions,
can be used on various types of terrain. In comparison, on-road
cars, which generally have a limited or non-existent suspension,
are strictly limited to smooth, paved surfaces.

Toy-grade radio control

The term "toy" or "toy-grade" in regards to radio control cars is
used to describe vehicles of the pre-assembled type generally found
in discount stores and consumer electronics stores. They are often
colloquially referred to as "Radio Shack cars". Some toy-grade R/C
models may also be found in hobby shops in an attempt to appeal to
young users. Generally speaking, a toy R/C is meant as a child's
plaything.

Advantages

Cost is the number one advantage of toy R/C vehicles. The average
medium-scale toy R/C car is around $50–$100 cheaper than an
entry-level electric hobby class vehicle. Toy class vehicles are
easy to operate, have a relatively low danger level (top speeds are
typically under 20mph, with most only capable of 10-15mph) and most
are even easier to set up than the simplest hobby class
ready-to-run vehicles (RTR's). Toy class vehicles are usually
modeled after real cars (most hobby class vehicles aren't), and
often feature details that hobby class vehicles lack, like working
lights, sounds, windows, opening doors and hoods, and realistic
interiors. Some also feature working sound systems with radios or
MP3 player inputs. There is also an almost endless array of toy R/C
vehicles, ranging from common cars and trucks, to tanks,
bulldozers, and motor cycles, to increasingly odd vehicles with
unorthodox designs.

Disadvantages

There are disadvantages to toy R/C vehicles – primarily crude
design and construction, poor performance, cheap hardware, and the
lack of spare parts. Toy R/C cars have very crude construction when
compared to even the most basic entry-level hobby class vehicles.
Most lack any form of a suspension and the ones that do feature a
suspension have very primitive or rudimentary designs. The same
goes for the electronics and radio system. Steering is typically
not proportional (with only three positions: straight, full left,
and full right) and there is typically no proportional "throttle"
either, with stopped and full power being the only options.
Performance is poor as well. Most are equipped with small, weak
motors and are powered by cheap alkaline or NiCd batteries which
means their top speed is usually only 10-15mph, and they have short
run times before new batteries are required. However, a new
lithium-ion polymer
battery has been developed. It comes with an electronic unit
and an on/off switch with LED lights that give
the status of the battery. It is lighter, smaller, and more
powerful than previous batteries. Toy R/C models are usually
limited to on road use only. Even models that are supposedly off
road oriented perform poorly off road. Toy R/C vehicles are meant
to be played with until they fail. They are difficult to repair and
replacement parts are almost impossible to come by. Stores selling
the vehicles rarely carry spare parts beyond replacement batteries
and chargers. Some basic parts may be available from the
manufacturer - both Tyco R/C and New Bright have a basic parts list enclosed with
their models - but they can be expensive and parts may take several
weeks to arrive from their Asian factories. Radio equipment, unlike
hobby-grade, is non-standardized and non-repairable unless one has
the necessary tools and equipment. Except for RadioShack's line of ZipZaps toy R/C cars, their XMODS line (which falls between toy- and hobby-grade),
and their recent Pro-Pulse series of cars (discontinued), no
aftermarket parts are available for toy
R/C, although an enterprising modeler may be able to retrofit
standard, discrete radio gear to them.

Hobby-grade radio control

In recent years, hobby-grade "ready-to-run" (or "RTR") models have
become available from every major manufacturer of radio-controlled
cars, attracting many hobbyists who would otherwise have purchased
a pre-assembled car (ARTR or Race-Roller). Vehicles of this type
need little or no final assembly and in many cases, the bodies are
shipped painted and trimmed, requiring little work from the owner
before they can be used (other than purchasing and installing
batteries). A number of cars and trucks are presently available
only in ready-to-run form. The growing popularity of the RTR
vehicle has prompted manufacturers to introduce kit versions of
their RTR cars that include factory upgrades but have no radio gear
installed and often no motor or speed controller.

Electric models

Electrically powered models utilize mechanical or electronic speed
control units to adjust the amount of power delivered to the
electric motor. The power delivered is proportional to the amount
of throttle called for by the transmitter - the more you pull the
trigger, the faster it goes. Mechanical speed controllers use a
network of resistors and switch between
them by rotating a head with an electrode
around a plate that has electrical contacts. Mechanical speed
controllers are prone to being slow to react, waste energy in the
form of heat from the resistors, and can
become dirty and perform intermittently, and lack a dedicated
braking ability. They are less expensive than high performance
electronic speed controls and usually ship in older hobby-grade
models. Electronic speed controllers use solid state components to regulate
duty cycle, adjusting the power delivered
to the electrical motor. In addition, most electronic speed
controllers use the electric motor as a magneticbrake, offering
better control of the model than is possible with a mechanical
speed control.

Most electric cars up to recently used brushed motors but now many
people are turning to brushless motors for their much higher power
and because they require much less maintenance. They are rated
either in turns or Kv. The Kv number tells how many RPM the motor
will turn per volt. However, the ability of the system to put out
power is dependent on the quality of the batteries used.Due to
their power, brushless motors are also used in bigger monster
trucks and 1/8 buggies that have been converted to electric.

Fuel models

Nitromethane fuel powered models utilize a servo for throttle and
braking control; rotation of the servo in one direction will cause
the throttle on the carburetor to open, providing more air and fuel
mixture to the internal
combustion engine. Rotation of the servo in the other direction
causes torque to be applied to a piece which
causes friction with the braking material. The brake is located on
the driveshaft and stops only two wheels
on a two-wheel drive car and all four wheels on a four-wheel drive
car.

Fuel engine sizes most often range between .12-.35 cubic inches. This is due to restrictions by
the main sanctioning bodies for radio-controlled racing. Many
"outlaw" engines are manufactured larger than these, mainly
intended for vehicles which will not be used in sanctioned races
and therefore do not need to comply with these regulations. Engine
size is related to the class of car; 1/10th scale on and off road
vehicles usually are equipped with .12-.18 cubic inch engines, with
1/8th scale vehicles using .21-.32 cubic inch engines.

Nitro-powered models

An Ofna Hyper 8 Pro 1:8-scale
nitro-powered racing buggy.

Fuel-powered engines allow model cars to reach moderate speeds
unmodified. Maximum power is generally achieved at medium to high
speeds, and a slightly slower throttle response than electrically
powered vehicles is to be expected. Electric motors effectively
produce instantaneous torque, whereas nitro engines, like
full-sized gasoline engines, take time for the engine to spool up
and for the clutch to engage. Nitro- (and fuel) powered cars may be
refueled and returned to action in a few seconds, as opposed to
electrics needing to remove the body shell and battery fasteners to
replace a discharged battery. Nitro cars are completely air cooled,
and may be run continuously with no need to take breaks for cooling
down. Nitro cars tend to be larger than electric cars on average,
because affordable high-performance electronics are only generally
available in 1:10 scale and smaller. However, scale equivalents do
exist in both nitro and electric forms.

Nitro-powered cars operate like full-sized fuel vehicles more than
their electric counterparts do, making use of a two stroke engine rather than an electric motor. The sound of the engine and
design of the drive train are main selling points to nitro
enthusiasts. However, their exhaust contains unburned oil, which
usually ends up coating the chassis. This, in turn, requires more
cleaning than an electric-powered equivalent. Cleaning is usually
achieved by the use of compressed air nozzles and solvents (such as
denatured alcohol). Tuning a
fuel-powered vehicle requires learning to maintain optimum
performance and fuel economy, and to minimize engine wear and
overheating, even in ready-to-run vehicles.

Because of higher stock performance and their ability to be driven
for longer periods of time, mechanical wear in nitro vehicles is
generally greater than in electric vehicles. In addition, the
increased speed and weight of fuel-powered vehicles generally lead
to higher speed collisions, causing greater damage to the collided
vehicles, and a greater degree of safety concerns needs to be taken
into account. However, nitro vehicles are more durable due to
stronger components to sustain the greater stresses of more
power.

Gas-powered models

Gasoline powered vehicles, also known as "fuelies" or "gassers",
run on premixed gasoline and oil. They cost much more (usually
$1000–$3000 RTR) than nitro and electric cars. They are also much
bigger and therefore require much more space to run. They don't
usually have high top end speeds (compared to nitro and some
electrics) but have lots of power and don't take a lot of fuel to
run. Over time the cost of a gas-powered car can be less than some
nitro-powered vehicles, because of the high cost of nitro fuel and
buying new nitro engines to replace worn-out ones. In addition,
gas-powered motors rarely if ever require tuning and have a very
long lifespan. These large scale models have been popular in Europe
for over a decade.

Accessories

All R/C models generally require the purchase of additional
accessories. For electrical vehicles, battery packs and a suitable
charger are needed to power the car.
A soldering iron and supplies are often necessary to build
high-performance battery packs and install upgraded electronics or
low-resistance plugs. For nitro-powered vehicles, a glow plug
heater and fuel are needed to start the engine, as well as 4 AA
size batteries, or a rechargeable 6-volt 5-cell battery pack to
power the onboard electronics. Nitro vehicles also require a means
of cranking the engine over, which can be achieved using a
pullstart, starterbox, battery operated rotostart, or by an
electric drill. Gasoline-powered vehicles require only a receiver
battery pack and a means to start the engine, usually a pullstart.
Hobby-grade vehicles almost always require 8 AA size batteries to
power the transmitter, though some can use rechargeable transmitter
pack, radios like the Futaba 3PKS.

A large industry of aftermarket manufacturers produce upgrade or
hop-up parts for hobby-grade cars. Upgrades range from mere
improvements to the longevity of R/C car parts, to all-out
performance enhancements. A number of hobbyists create their own
upgrades for sale via classifieds and online forums.

"Ready-to-run" cars can be purchased, which leave the factory in a
pre-tuned condition that affords for good racing performance
without prior adjustment. However, those vehicles should still be
inspected for loose parts prior to operation as stated in many
manuals.Alternatively, vehicles can be purchased that are either in
kit form or are partially assembled, which are built and tuned by
the owner prior to use, but most of the time, the owner will have
to buy radio gear, and sometimes even an engine when they buy a
kit.

Principles of operation

Radio-controlled cars use a common set of components for their
control and operation. All cars require a transmitter, which has the joysticks for
control, or in pistol grip form, a trigger for throttle and a wheel
for turning, and a receiver which
sits inside the car. The receiver changes the radio signal broadcast from the transmitter into
suitable electrical control signals for the other components of the
control system. Most radio systems utilize amplitude modulation for the radio
signal and encode the control positions with pulse width modulation. Upgraded
radio systems are available that use the more robust frequency modulation and pulse code modulation. The radio is
wired up to either electronic
speed controls or servomechanisms (shortened to "servo" in
common usage) which perform actions such as throttle control,
braking, steering, and on some cars, engaging either forward or
reverse gears. Electronic speed controls and servos are commanded
by the receiver through pulse width modulation; pulse duration sets
either the amount of current that
an electronic speed control allows to flow into the electric motor
or sets the angle of the servo. On the models the servo is attached
to at least the steering mechanism; rotation of the servo is
mechanically changed into a force which steers the wheels on the
model, generally through adjustable turnbuckle linkages. Servo
savers are integrated into all steering linkages and some nitro
throttle linkages. A servo saver is a flexible link between the
servo and its linkage that protects the servo's internal gears from
damage during impacts or stress.

History

Racing model in Hrotovice race.

An 1:8 four-wheel drive off-road
racing buggy in action

The beginnings of model racing

Small, nitromethane-powered engines
originally entered the market in the 1940s. At the time with the
ability for precise control in a similar manner as with a
vehicle.

Early commercial products

Several early commercially viable R/C cars were available by
mid-1960, produced by the Italian company El-Gi (Elettronica
Giocattoli) from Reggio Emilia. Their first model, a 1:12 Ferrari
250LM was available in the UK in December 1966, through importers
Motor Books and Accessories, St. Martins, London, and early in 1967
through Atkinson's model shop in Swansea. This model was followed
by El-Gi's 1:10 Ferrari P4, first shown at the Milan Toy Fair in
early 1968.

In the mid-late 60s a British company, Mardave, based in Leicester,
began to produce commercially viable RC Cars. Their first cars were
nitro- or gas-powered cars sold in the local area in the early
70s.

In the early 70s several commercial products were created by small
firms in the US. Most of these companies began as slot car
companies and with the wane in popularity of that genre moved into
the R/C field. Among these were Associated Electrics, Thorp,
Dynamic, Taurus, Delta, and Scorpion. These early kits were 1/8
scale nitro-powered (then called gas) aluminum flat pan cars
powered by a .21 or smaller engine. The bodies for these cars were
made of polycarbonate (the most popular made of Lexan). The most
popular engine was the K&B Veco McCoy. The primary sanctioning
body for races for these cars was Remotely Operated Auto Racers
(ROAR).In 1973-74, Jerobee, a company based in Washington State,
created their 1/12 nitro car using a Cox .049 engine. Several
aftermarket companies created parts for this car including clear
Lexan bodies, heat sinks, and larger fuel tanks. This scale evolved
into 1/12 scale electric racing when Associated Electrics created
the RC12E in 1976-77. Jerobee became Jomac and created their own
electric kit.

By the late 1970s, interests in 1/12 scale electric racing began to
grow as 1/8th scale IC racers, the sole racing category at the
time, needing to race throughout the winter as an alternative to
their impractical IC cars began to race 1/12 cars, therefore a
winter national series was developed. As a result, the series grew
into popularity as a large number of scratchbuilt cars started to
appear in these meetings.

In 1976, the Japanese firm Tamiya, which was
renowned for their intricately detailed plastic model kits,
released a series of elegant and highly detailed, but mechanically
simple electric on-road car models that were sold as "suitable for
radio control". Although rather expensive to purchase, the kits and
radio systems sold rapidly. Tamiya soon began to produce more
purpose-built remote-controlled model cars, and were the first to
release off-road buggies featuring real suspension systems. It was
this progression toward the off-road class that brought about much
of the hobby's popularity, as it meant radio-controlled cars were
no longer restricted to bitumen and smooth surfaces, but could be
driven virtually anywhere. The first true Tamiya off road vehicles
were the Sand Scorcher and the
Rough Rider, both released in
1979, and both based on realistic dune buggy designs.Tamiya
continued to produce off road vehicles in increasing numbers,
featuring working suspensions, more powerful motors, textured
off-road rubber tires and various stylized "dune buggy" bodies. They also produced trucks,
such as the Toyota HiLux Pickup, that featured realistic 3 speed
gearboxes and leaf-spring suspension systems. All of these models
were realistic, durable, easy to assemble, capable of being
modified, and simple to repair. They were so popular that they
could be credited with launching a boom in radio-controlled model
cars in the early to mid 1980s, and provided the basis for today's
radio-controlled car market. Popular Tamiya models included the
Grasshopper and the Hornet dune buggies as well as the Blackfoot
and Clodbuster monster truck models.
The earliest Tamiya models, particularly the early off roaders, are
now highly sought after by vintage R/C collectors and can fetch
prices of up to US$3000 on internet auction sites if still in mint,
unbuilt form. Acknowledging their continued popularity, several of
the early kits have even been re-released by Tamiya during
2005–2007, with a few alterations.

A British firm, Schumacher Racing,
was the first to develop an adjustable ball differential in 1980, which allowed
nearly infinite tuning for various track conditions. At the time
the majority of on-road cars had a solid axle, while off-road cars
generally had a gear-type differential. Team Associated followed suit with the
introduction of the RC10 off-road racing buggy in 1984 (see
below)

Modern developments in radio controlled racing

Modified 1/8 scale buggy with upper
body removed

In 1984,
Associated Electrics, Inc. of
Costa Mesa,
California introduced the RC10
off-road electric racer; this model was a departure from Associated
Electrics' regular line of nitromethane-powered on-road race
cars. Designed as a high-grade radio controlled car, the
chassis of the RC10 buggy was manufactured from anodised,
aircraft-grade aluminiumalloy. The shock
absorbers were machined, oil-filled and completely tuneable;
they were also produced from the same aluminium alloy. Suspension
control arms were manufactured from high-impact nylon, as were the three-piece wheels.

Optional metal shielded ball bearings were sometimes incorporated
in RC10 wheels and transmissions. The RC10
transmission contained an innovative differential featuring
hardened steel rings pressed against balls - which made it almost
infinitely adjustable for any track condition. The RC10 quickly
became the dominant model in electric off-road racing.

In 1986, Schumacher Racing Products released their CAT (Competition
All Terrain) vehicle, widely considered the best four wheel drive off-road "buggy" racer of
the time. The CAT went on to win the 1987 off-road world
championship. This car is credited for sparking an interest in
four-wheel-drive electric off-road racing.

Gil Losi
Jr., whose family ran the "Ranch Pit Shop R/C" racetrack in
Pomona,
California, turned his college studies toward engineering,
primarily in the field of injection
molded plastics, leading to his foundation of Team Losi. When the JRX-2, the
first Team Losi buggy, was released, it
initiated a rivalry with Team Associated that continues to this
day. Team Losi went on to secure a number of achievements, which
included the industry's first all-natural rubber tires, the first
American-made four-wheel-drive racing buggy, and an entirely new
class of cars, the 1/18-scale Mini-T
off-road electrics.

Although Losi and Associated seemed to dominate much of the
American market, Traxxas, (another American
company, famous for the T-MAXX and the REVO 3.3), and Kyosho (from Japan), were also making competitive
two-wheel-drive off-road racing models. Although Losi and
Associated were close rivals in the USA, Schumacher off-road models
continued to be popular amongst European hobbyists.

Electric and nitro cars have come a long way in terms of power.
Electric cars have gone from non-rebuildable brushed motors and
ni-cad batteries to brushless motors and LiPo. Nitro cars have gone from
small engines to huge .32 engines that are used in big monster
trucks.